From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx144.postini.com [74.125.245.144]) by kanga.kvack.org (Postfix) with SMTP id CF90C6B004D for ; Tue, 17 Apr 2012 06:08:43 -0400 (EDT) Message-ID: <1334657287.28150.77.camel@twins> Subject: Re: [PATCH 2/6] uprobes: introduce is_swbp_at_addr_fast() From: Peter Zijlstra Date: Tue, 17 Apr 2012 12:08:07 +0200 In-Reply-To: <20120416153408.GA8852@redhat.com> References: <20120405222024.GA19154@redhat.com> <20120405222106.GB19166@redhat.com> <1334570935.28150.25.camel@twins> <20120416144457.GA7018@redhat.com> <1334588109.28150.59.camel@twins> <20120416153408.GA8852@redhat.com> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: quoted-printable Mime-Version: 1.0 Sender: owner-linux-mm@kvack.org List-ID: To: Oleg Nesterov Cc: Ingo Molnar , Srikar Dronamraju , Andrew Morton , Linus Torvalds , Ananth N Mavinakayanahalli , Jim Keniston , LKML , Linux-mm , Andi Kleen , Christoph Hellwig , Steven Rostedt , Arnaldo Carvalho de Melo , Masami Hiramatsu , Thomas Gleixner , Anton Arapov On Mon, 2012-04-16 at 17:34 +0200, Oleg Nesterov wrote: > On 04/16, Peter Zijlstra wrote: > > > > Can't we 'optimize' read_opcode() by doing the pagefault_disable() + > > __copy_from_user_inatomic() optimistically before going down the whole > > gup()+lock+kmap path? >=20 > Unlikely, the task is not current. Easy enough to test that though.. and that should make the regular path fast enough, no? --- kernel/events/uprobes.c | 9 +++++++++ 1 files changed, 9 insertions(+), 0 deletions(-) diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index 985be4d..7f5d8c5 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -312,6 +312,15 @@ static int read_opcode(struct mm_struct *mm, unsigned = long vaddr, uprobe_opcode_ void *vaddr_new; int ret; =20 + if (mm =3D=3D current->mm) { + pagefault_disable(); + ret =3D __copy_from_user_inatomic(opcode, (void __user *)vaddr,=20 + sizeof(*opcode)); + pagefault_enable(); + if (!ret) + return 0; + } + ret =3D get_user_pages(NULL, mm, vaddr, 1, 0, 0, &page, NULL); if (ret <=3D 0) return ret; -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org